netdev - Re: [PATCH net-next v2 0/7] net: stmmac/xpcs: modernise PCS support

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Message-ID: <CA+V-a8ve+6XPgWAQDJNwzG9ox-BSNqOBrO6JU7dL=yfQPgP0Ag@mail.gmail.com>
Date: Fri, 17 Oct 2025 18:02:28 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Giuseppe Cavallaro <peppe.cavallaro@...com>, Jose Abreu <Jose.Abreu@...opsys.com>, 
	Maxime Coquelin <mcoquelin.stm32@...il.com>, Andrew Lunn <andrew@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Heiner Kallweit <hkallweit1@...il.com>, 
	Jakub Kicinski <kuba@...nel.org>, Jose Abreu <joabreu@...opsys.com>, 
	linux-arm-kernel@...ts.infradead.org, 
	linux-stm32@...md-mailman.stormreply.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 0/7] net: stmmac/xpcs: modernise PCS support

On Fri, Oct 17, 2025 at 6:00 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
>
> Hi,
>
> On Wed, Jan 26, 2022 at 10:32 AM Russell King (Oracle)
> <linux@...linux.org.uk> wrote:
> >
> > Hi,
> >
> > This series updates xpcs and stmmac for the recent changes to phylink
> > to better support split PCS and to get rid of private MAC validation
> > functions.
> >
> > This series is slightly more involved than other conversions as stmmac
> > has already had optional proper split PCS support.
> >
> > The first six patches of this series were originally posted on 16th
> > December for CFT, and Wong Vee Khee reported his Intel Elkhart Lake
> > setup was fine the first six these. However, no tested-by was given.
> >
> > The patches:
> >
> > 1) Provide a function to query the xpcs for the interface modes that
> >    are supported.
> >
> > 2) Populates the MAC capabilities and switches stmmac_validate() to use
> >    phylink_get_linkmodes(). We do not use phylink_generic_validate() yet
> >    as (a) we do not always have the supported interfaces populated, and
> >    (b) the existing code does not restrict based on interface. There
> >    should be no functional effect from this patch.
> >
> > 3) Populates phylink's supported interfaces from the xpcs when the xpcs
> >    is configured by firmware and also the firmware configured interface
> >    mode. Note: this will restrict stmmac to only supporting these
> >    interfaces modes - stmmac maintainers need to verify that this
> >    behaviour is acceptable.
> >
> > 4) stmmac_validate() tail-calls xpcs_validate(), but we don't need it to
> >    now that PCS have their own validation method. Convert stmmac and
> >    xpcs to use this method instead.
> >
> > 5) xpcs sets the poll field of phylink_pcs to true, meaning xpcs
> >    requires its status to be polled. There is no need to also set the
> >    phylink_config.pcs_poll. Remove this.
> >
> > 6) Switch to phylink_generic_validate(). This is probably the most
> >    contravertial change in this patch set as this will cause the MAC to
> >    restrict link modes based on the interface mode. From an inspection
> >    of the xpcs driver, this should be safe, as XPCS only further
> >    restricts the link modes to a subset of these (whether that is
> >    correct or not is not an issue I am addressing here.) For
> >    implementations that do not use xpcs, this is a more open question
> >    and needs feedback from stmmac maintainers.
> >
> > 7) Convert to use mac_select_pcs() rather than phylink_set_pcs() to set
> >    the PCS - the intention is to eventually remove phylink_set_pcs()
> >    once there are no more users of this.
> >
> > v2: fix signoff and temporary warning in patch 4
> >
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 147 +++++++---------------
> >  drivers/net/pcs/pcs-xpcs.c                        |  41 +++---
> >  include/linux/pcs/pcs-xpcs.h                      |   3 +-
> >  3 files changed, 73 insertions(+), 118 deletions(-)
> >
> Although RZ/V2H doesn't have PCS, it tested this on Renesas RZ/V2H EVK
> and found no regressions.
>
Ouch wrong series, retracting the Tested-by.

Cheers,
Prabhakar